Fluid pressure operated devices for radially expanding portions of tubing are known, such devices being disclosed in U.S. Pat. Nos. 1,448,457; 2,479,702; 2,938,562; and 3,200,627. Structures of these patents include fluid conveying mandrels receivable within the tubes, means for expanding the mandrels to hold the tubing, and die elements against which portions of the tubing are flared or otherwise formed by fluid pressure. These expanding devices are customarily used to provide short bulges in tubing for coupling purposes and the like. In addition, they are used to expand tubing to fit fins and other apparatus connected to the outer surface of the tubing.
Several hydraulic chucks have been developed which are suitable for tightly gripping one end of the elongated tube while simultaneously delivering a tube expanding fluid. Among these are U.S. Pat. Nos. 3,505,846; 3,813,751; and 3,962,769.
One of the problems which continuously plague those users of hydraulic chucks is the failure of seals after only a few operations of the hydraulic chuck. Various means have been developed to allow the user to temporarily connect a fluid system to a conductor such as in the process for hydrostatic testing of pipe, or in the placements of fins on air-conditioning tubing. All of these means use conventional, fixed, elastomeric seals to seal the connector or hydraulic chuck to the conductor or tube. While this results in an initially workable seal, it is often extremely shortlived due to damage inflicted by the rough end of the tube when the chuck is installed on the tubing. When the tubing is tested or is expanded for other purposes, the pressure within the system is oftentimes quite high. Thus, the seals are necessary to prevent passage or fluid into areas which would cause leaks, and more importantly the pressure must be maintained to accomplish its objectives.
Accordingly, it is an object of this invention to provide a tube engaging chuck which is capable of maintaining adequate sealing through competitive uses. Another object of this invention is to provide a chuck which can readily grip the tube to be expanded, permitting preloading of the tube prior to the expansion. This is a particular advantage in complicated assemblies where a large tube or a multiplicity of tubes are being expanded in an apparatus wherein the relationship spacially of one tube to another is critical. By being able to preload the tubes with fluid, it is possible to rearrange and restructure the relative relationships of the tubes immediately prior to expansion without any surge occuring from the addition of fluid to the tubes themselves.